Introduction; The Kn-Series V3 Heatnet Control - HydroTherm HeatNet KN -6 User Information

FEATURES & SPECIFICATIONS

Introduction

The KN-Series V3 HeatNet Control

The KN-Series V3 boiler control is the third generation of
the HeatNet control platform. Control hardware has been
added to make use of many new heating applications. These
new features are outlined in the Features & Specifications
section.
The KN-Series boiler control is designed to provide the KN-
Series of boilers with an integrated boiler management
system on every boiler. Designed for the Air-Fuel coupled
KN-Series boilers, the KN-Series HeatNet control provides
for optimized heating efficiency without the need for a ―wall
mount control‖. Since the KN-Series modular control
method is based on digital communications, analog control
signals are not required. Although the use of analog control
signals is still supported (4-20mA control loops and 0-10vdc
control voltages), a higher level of control precision,
repeatability, and feedback is gained with digital
communications control.
With the KN-Series, optimized heating efficiency is
accomplished by setting the Modulation Maximum (Mod-
Max) setting to exploit the inverse efficiency curve. This
value can be adjusted so that as each boiler is added, it
operates at its maximum turndown. This allows the
maximum number of boilers to operate at their lowest
inputs, until all boilers are firing. Once all boilers are firing,
full range modulation control is allowed. An outdoor reset
function is also provided to assist in the optimized heating
efficiency of the KN-Series boilers.
The KN-Series boiler with the KN-Series H-Net control, can
be operated in multiple ways:
1. As a stand-alone boiler.
2. A boiler in a Boiler Network using the HeatNet
®
(H-Net ) protocol.
3. A member boiler to a boiler management system with
multiple input control methods.
The primary purpose of the control is to maintain the boiler
water temperature at the supply or the header sensor using a
target setpoint. While performing this task, the control also
monitors dedicated external limits in a limit string and
provides an orderly shutdown and fault indication in the
event of a tripped limit. The monitored limits include a
HIGH LIMIT AQUASTAT, LOW WATER CUTOFF,
GAS PRESSURE, FLOW, IGNITION CONTROL fault,
GAS VALVE alarm, VARIABLE FREQUENCY DRIVE
alarm, and other optional or user selectable limits.
Each KN-Series boiler employing this control can function
as either a master or a member. This allows one boiler
(Master) to be in control of target temperature. The other
boilers (Members) only respond to the commands issued by
the Master. If using an external control, all boilers can be
setup as members. The following will define the roles of
master and member.
Master
A boiler becomes a master when a temperature sensor is
connected to the J10 ―SYSTEM HEADER‖ terminals. The
sensor is auto-detected.
The master senses and controls the common system
header/loop water temperature using a system setpoint. It
uses any boilers it finds (over the H-Net communications
cable) to accomplish this. It can also monitor the Outside
Air (OA) temperature to provide outdoor reset functionality.
Only one master is allowed in a system.
When operating as a master, the boiler provides a control
method using a PID algorithm to regulate water
temperature. This algorithm allows a single boiler (Master),
or multiple (Master + Member) boilers.
Figure 1
UPPER HEAT
BAND LIMIT
SETPOINT
LOWER HEAT
®
BAND LIMIT
WATER
TEMPERATURE
The control algorithm is based upon a Heat Band, at the
center of which is the setpoint. While below the Heat Band,
boilers are staged on and modulated up until the Heat Band
is entered. Once in the Heat Band, modulation is used to
maintain setpoint. Boilers are shut down only when the top
of the Heat Band is breached. Timers are also used to
prevent short cycling.
While staging the boilers on, a modulation clamp
ADVANCED SETUP: MODULAR BOILER SET:
MOD MAX-LAST FIRE is used to hold the boilers at a
lower fire rate until the last boiler is fired. Once the last
boiler fires, the modulation clamp is removed and all boilers
are allowed to fire above this clamped percentage up to
HeatNet Control V3 2.x
The HIGH LIMIT circuit is independent of
the control and shuts down the ignition
control and the boiler if the control board or
other component of the boiler was to
malfunction. The control will continue to
function and report the fault, but its ability to
control the boiler will end.
Heat band
BOILERS
STAGED
OFF
Boilers Staged
ON
Time
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